Gemellus Superior: Origin, Insertion, Nerve & The "Upper Twin"

The Gemellus Superior is a small muscle of the posterior hip, lying deep to the Gluteus Maximus. Its name comes from the Latin for "Twin" (Gemellus), referring to its pairing with the Gemellus Inferior. It is part of the "Short External Rotator" group, which functions like the rotator cuff of the shoulder to stabilize the hip joint.

[Image of Gemellus Superior muscle anatomy]

Quick Anatomy Snapshot

Origin (Proximal)	External surface of the Ischial Spine.
Insertion (Distal)	Medial surface of the Greater Trochanter of the Femur (blending with the Obturator Internus tendon).
Nerve Supply	Nerve to Obturator Internus (L5, S1).
Blood Supply	Inferior Gluteal Artery and Internal Pudendal Artery.
Primary Actions	External Rotation: Rotates the extended thigh laterally. Abduction: Abducts the flexed thigh. Stabilization: Secures the femoral head in the acetabulum.

Deep Dive: The Triceps Coxae

The Gemellus Superior is rarely mentioned without its partners. Together, they form a unique functional unit.

1. The "Three-Headed" Hip Muscle

The Triceps Coxae is not a single muscle, but a term used to describe the fusion of three muscles:
1. Gemellus Superior (Top).
2. Obturator Internus (Middle).
3. Gemellus Inferior (Bottom).
The Obturator Internus tendon acts as the core, while the Gemelli merge into it from above and below as it exits the pelvis, creating a powerful composite tendon.

2. The Nerve Difference

This is a crucial distinction for students:
• Gemellus Superior shares innervation with the Obturator Internus (Nerve to Obturator Internus).
• Gemellus Inferior shares innervation with the Quadratus Femoris (Nerve to Quadratus Femoris).
Even though they are "twins," they are supplied by different nerves.

Physio Corner: Clinical Relevance

💪 Functional Fact: During the swing phase of walking, the Gemelli help fine-tune the position of the leg, rotating it so the foot lands correctly. In the stance phase, they compress the hip joint to provide stability.

Palpation

Because it lies deep to the Gluteus Maximus and Sciatic Nerve, direct palpation is difficult. It is located between the Posterior Superior Iliac Spine (PSIS) and the Ischial Tuberosity. Deep pressure here usually elicits tenderness in patients with Deep Gluteal Syndrome.

⚠️ Clinical Pathology: Snapping Hip (Posterior)
While less common than IT band snapping, the conjoint tendon of the Triceps Coxae (Obturator Internus + Gemelli) can sometimes snap over the posterior acetabulum, causing pain and an audible click in the deep buttock.

Manual Muscle Testing (MMT)

The Gemelli are tested as part of the External Rotator group.

Testing Tip: Testing in sitting (hip flexion) biases the Obturator Internus and Gemelli over the Quadratus Femoris and Gluteus Maximus.

Step-by-Step Procedure (Oxford Scale)

Grade	Patient Action & Resistance
Grade 3, 4, 5 (Against Gravity)	Position: Short sitting (legs dangling off edge of table). Action: Patient moves the foot medially (which rotates the hip laterally/externally). Resistance: Applied just above the medial malleolus (ankle), pushing the foot laterally (into internal rotation). Grade 3: Full range. Grade 4/5: Holds against moderate/max resistance.
Grade 2 (Gravity Eliminated)	Position: Supine. Leg extended and internally rotated. Action: Patient rolls the leg outward (toes point out). Result: Full range of external rotation.
Grade 0, 1 (Palpation)	Action: Deep palpation posterior to the Greater Trochanter. Cue: "Try to turn your thigh out." Grade 1: Deep tension felt (hard to isolate). Grade 0: No activity.

Frequently Asked Questions

Why is it called "Superior"?

Because it lies superior (above) the tendon of the Obturator Internus. Its origin (Ischial Spine) is anatomically higher than the origin of the Inferior Gemellus (Ischial Tuberosity).

Is Gemellus Superior part of the pelvic floor?

No. While it is located in the gluteal region near the pelvis, it is a hip muscle acting on the femur, not a pelvic floor muscle (like the Levator Ani).

Does it act as an abductor?

Yes, but only when the hip is flexed. When the hip is extended, it is purely an external rotator.

Test Your Knowledge: Gemellus Superior Quiz

1. Which nerve supplies the Gemellus Superior?

2. What is the origin of the Gemellus Superior?

3. The Gemellus Superior lies immediately superior to which structure?

4. Where does the Gemellus Superior insert?

5. The primary action of Gemellus Superior on an extended hip is:

6. The Gemelli muscles are often described as extra heads of which muscle?

7. Which vessel provides blood supply to the Gemellus Superior?

8. The Gemellus Superior passes through which foramen as it leaves the pelvis?

9. When the hip is flexed, what secondary action does Gemellus Superior perform?

10. True or False: The Sciatic nerve runs deep (anterior) to the Gemellus Superior.

References

• Moore, K. L., Dalley, A. F., & Agur, A. M. R. (2018). Clinically Oriented Anatomy. 8th ed. Philadelphia: Wolters Kluwer.
• Standring, S. (2016). Gray's Anatomy: The Anatomical Basis of Clinical Practice. 41st ed. Elsevier.
• Travell, J. G., & Simons, D. G. (1999). Myofascial Pain and Dysfunction: The Trigger Point Manual. 2nd ed. Williams & Wilkins.